The present invention relates generally to the art of transparent metallic films for solar energy control, and more particularly to the art of sputtering silver-containing films.
Transparent metallic films for solar energy control may be prepared by wet chemical deposition processes which involve solutions of metallic ions which are chemically reduced by reducing agents to form metallic films. Transparent films of metals such as silver, copper, nickel and cobalt are readily produced by such methods. U.S. Pat. No. 3,457,138 to Miller discloses an electroless (wet chemical) method for producing transparent copper films over a thin transparent silver film on glass. Similarly produced wet chemical silver/copper films on glass have achieved commercial success as solar energy control architectural products. The coating effectively reflects solar heat energy while presenting an aesthetically appealling low reflectance pinkish colored surface to the observer.
Advances in coating technology provide alternative processes such as chemical vapor deposition, vacuum evaporation deposition, and cathode sputtering for producing transparent metallic flims for solar energy control. Cathode sputtering is particularly desirable for producing metallic films in a method that is fast and efficient on a large scale. U.S. Pat. No. 4,166,018 to Chapin discloses a particularly useful sputtering process and apparatus which employ a magnetic field to improve cathode sputtering conditions.
In an attempt to reproduce the properties of a wet chemical two-layer silver/copper film on glass by cathode sputtering, it was discovered that, using known cathode sputtering techniques to produce two-layer silver/copper films over a variety of thicknesses and thickness ratios, the desirable low reflectance pinkish colored appearance of the wet chemical two-layer silver/copper film could not be obtained. Rather, typical sputtering conditions result in two-layer silver/copper films that range in appearance from highly reflective bright silver to highly reflective bright copper depending on the silver/copper ratio and the orientation of the sample.